Identification and allergenic activity of hydroxyaldehydes - a new type of oxidation product from an ethoxylated non-ionic surfactant.

Ethoxylated alcohols, which are widely used as surfactants, are susceptible to oxidation on air exposure. A complex mixture of oxidation products is formed, among which alkylated aldehydes, alkylated formates, formaldehyde and peroxides have previously been identified by our group. In the present study, we have identified a new class of oxidation product from the nonionic ethoxylated surfactant C12E5. These oxidation products are highly water-soluble hydroxyaldehydes with the general formula HO(CH2CH2O)nCH2CHO, n=1-4. To facilitate the identification of the hydroxyaldehydes in oxidized C12E5, reference compounds were synthesized. The sensitizing potential of 1 of the identified hydroxyaldehydes, HO(CH2CH2O)3CH2CHO, was studied in guinea pigs and was found to be weak. A significant cross-reactivity between this aldehyde and the next shorter homologue, HO(CH2CH2O)2CH2CHO, was observed. Irritant components, present in the oxidation mixture, facilitate the skin penetration of allergens, which further accentuates the importance of controlling the conditions of storage and handling of ethoxylated surfactants, to reduce the formation of allergenic and irritant oxidation products.

Atmospheric oxidation of poly(oxyethylene) alcohols. Identification of ethoxylated formates as oxidation products and study of their contact allergenic activity.

Ethoxylated alcohols are widely used as surfactants. In the present study we have continued our investigations on the degradation with time upon air exposure of the ethoxylated alcohols at normal storage and handling. As a result, a new group of ethoxylated formates with the general formula C12H25(OCH2CH2)nOCHO (n = 0-4) was identified in C12H25(OCH2CH2)5OH stored and handled at room temperature. To facilitate the identification work, reference compounds were synthesized. The formates showed no allergenic activity in the sensitization studies performed. In previous investigations on the same ethoxylated alcohol, we have identified formaldehyde and ethoxylated aldehydes among the oxidation products formed. Formaldehyde is a common contact allergen, and the ethoxylated aldehydes were shown to have a sensitizing capacity of the same magnitude as formaldehyde. The instability of the ethoxylated alcohols and formation of oxidation products may give an allergenic contribution to hand eczema caused by work with water and surfactants. To investigate the clinical significance in man an appropriate diagnostic patch testing in exposed humans is required.

Contact allergens from surfactants. Atmospheric oxidation of polyoxyethylene alcohols, formation of ethoxylated aldehydes, and their allergenic activity.

Ethoxylated surfactants are susceptible to oxidation upon air exposure. We have previously studied the rate of peroxidation and formaldehyde formation in the chemically well-defined ethoxylated alcohol C12H25(OCH2CH2)5OH. Formaldehyde is a common cause of contact allergy. The aim of the present study was to identify other oxidation products that could be formed upon air exposure of the ethoxylated alcohol and to determine their allergenic activity. It was shown that air oxidation of C12H25(OCH2CH2)5OH gave all the theoretically possible aldehydes of the general formula C12H25(OCH2CH2)nOCH2CHO (n = 0-4) and that the major oxidation product was C12H25(OCH2CH2)4OCH2CHO, dodecyltetraoxyethyleneoxyacetaldehyde. The structure elucidation and synthesis of these aldehydes are here presented for the first time. The major aldehyde was shown to be a contact allergen with the same sensitizing capacity as that of formaldehyde. A dose-response relationship was observed in the sensitization studies. The allergens were formed from the surfactant itself and the skin reactions cannot be explained due to any impurities that may be present in a technical quality of the surfactant. Cases of allergic contact dermatits to ethoxylated surfactants have been reported. To avoid the formation of allergenic oxidation products it is important to control the conditions for storage, handling, and transportation of ethoxylated surfactants.

15-hydroperoxydehydroabietic acid--a contact allergen in colophony from pinus species.

A new hydroperoxide, 15-hydroperoxydehydroabietic acid (15-HPDA), with contact allergenic properties has been detected in rosin obtained from Pinus species. Detection was facilitated using a synthetic preparation of 15-HPDA for reference purposes. The synthesis and the detection (HPLC and GC) of 15-HPDA in rosin are described. The allergenic activity of 15-HPDA was studied in an experimental sensitization test on guinea-pigs.

Allergenicity of rosin (colophony) esters (II). Glyceryl monoabietate identified as contact allergen.

In the esterification of rosin with glycerol, the main compound formed, glyceryl triabietate, shows low allergenic activity. In this study, compounds formed in smaller amounts, when abietic acid (main component in rosin) was esterified with glycerol, were identified as glyceryl-1-monoabietate (GMA), glyceryl-1,2-diabietate (GDA1,2) and glyceryl-1,3-diabietate (GDA1,3), using nuclear magnetic resonance (NMR), infra-red (IR) and mass spectrometry (MS) analyses. According to animal experiments, GMA was a contact allergen. No cross-reactivity was seen to allergens in unmodified rosin. Some patients allergic to unmodified rosin reacted when tested with GMA. No reactions were seen to the 2 diabietates. Some patients also reacted to commercial glycerol-modified rosins. GMA together with unmodified abietic acid were identified in these rosin samples. The reactions seen in rosin-sensitive patients to commercial glycerol-esterified rosins probably derive from the unmodified material still present in the product, but could also be the result of GMA obtained from the glycerol derivatization.

Contact allergy to resin acid hydroperoxides. Hapten binding via free radicals and epoxides.

For a better understanding of the mechanisms of contact allergic reactions, the patterns of cross-reactivity between different resin acid oxidation products were studied. The 13,14(alpha)-epoxide and the 13,14(beta)-epoxide of abietic acid and 15-hydroperoxydehydroabietic acid (15-HPDA) were shown in experimental sensitization studies to be contact allergens. Cross-reactivity was observed between the alpha- and beta-epoxides and also between the epoxides and the previously identified rosin allergen 15-hydroperoxyabietic acid (15-HPA). This indicates that 15-HPA may form an epoxide which then reacts with skin protein to generate the complete antigen. 15-HPA and 15-HPDA cross-reacted as well. This can be explained by the formation of similar alkoxy radicals from both hydroperoxides which further react with skin protein. Cross-reactivity patterns of the resin acid oxidation products indicate that 15-HPA may react with skin proteins either as a radical or as an epoxide, thus generating different antigens. The presence in rosin of the epoxides of abietic acid was also studied. The beta-epoxide was detected in gum rosin. Moreover, the epoxides elicited reactions in rosin-allergic individuals. Thus, the 13,14(beta)-epoxide of abietic acid was identified as a new, important rosin allergen.

Hydroperoxides in oxidized d-limonene identified as potent contact allergens.

Hydroperoxides of d-limonene were shown to be potent contact allergens when studied in guinea-pigs. Limonene-2-hydroperoxide (2-hydroperoxy-p-mentha-6,8-diene, a mixture of trans and cis isomers) was synthesized for the first time. The ratio between the trans and cis forms was 3:1. These two hydroperoxides were identified as the major hydroperoxides in autoxidized d-limonene. In photo-oxidized d-limonene, they constituted a minor part of the hydroperoxide fraction. Hydroperoxides may bind to proteins of the skin to make antigens either via a radical mechanism or after reactions to give epoxides. The cross-reactivity between the epoxide limonene-1,2-oxide, a potent contact allergen, and the hydroperoxides was therefore studied. No significant pattern of cross-reactivity was found. Further studies to identify and test the allergenicity of single hydroperoxides are needed to elucidate the mechanism of the allergenicity.

The allergenicity of glycerol esters and other esters of rosin (colophony).

To investigate whether esterification of rosin with polyalcohols changes its allergenic potential, abietic acid, the main component of rosin, was esterified with glycerol at high temperature. The major product formed was isolated and identified, using nuclear magnetic resonance (NMR), infra-red (IR) and mass spectrometry (MS) analyses, as glyceryl triabietate (GTA), an ester between one glycerol molecule and 3 abietic acid molecules. According to animal experiments GTA was not allergenic and no cross-reactivity was seen to allergens in unmodified rosin. When testing patients allergic to unmodified rosin, no reactions were found to GTA. Some of the patients reacted to glycerol- and pentaerythritol-esterified rosins. According to HPLC analyses, these esterified rosins still contained unmodified material to which the patients may have reacted. It seems that the esterification of rosin with polyalcohols such as glycerol reduces its allergenic activity, possibly because of the formation of much larger molecules with reduced bioavailability. However, making methyl esters of rosin causes little alteration in the molecular weights of the components and, when unmodified and methylated rosin were tested in patients, we saw no difference between the 2 forms.